Beltsville researchers have been doing research
related to organic farming systems for more than
ten years. But how has National Organic Program
implementation in 2002 affected the research context?
How much certified organic research is going forward
at BARC, and at ARS generally?
Carolee Bull, a research plant pathologist based
at an ARS station in Salinas, California, has
been cooperating with Mike Jawson, ARS National
Program Leader for Integrated Farming Systems,
and others to find answers to those questions.
Bull reports that there is now a total of about
70 certified organic acres at ARS research stations
in Iowa, Maryland, California, Florida, Texas,
Georgia, and Minnesota. An unknown additional
amount of land is probably readily certifiable.
A key stop on Teasdale's BARC field tour is a
22-acre field that recently became the center's
first certified organic research acreage. This
spring, Teasdale and his colleagues established
their first experimental plots on the site, a
study of weed tolerance by organic soybeans with
different growth habits.
A total of six cultivars, some of them developed
here at BARC by geneticist Tom Devine, are being
evaluated in paired plots: a tall soybean vs.
a standard-height soybean; an early developing
soybean vs. a standard developer; and a large
leaf vs. a normal-sized leaf. All plots are receiving
identical cultivation treatments between the rows,
but the in-row area—where weeds are most
difficult to manage—is being subjected to
three different treatments: all weeds are removed;
crop plants removed; and additional weed seeds
Although the facility in Salinas is so far the
only ARS station with a dedicated organic specialist
position—research horticulturalist Eric
Brennan—Teasdale notes that his lab and
others began collaborating with local certified
organic farmers as early as 1999. That strategy
continues: Teasdale's lab is currently participating
in an organic high-tunnel tomato production evaluation,
funded in part by SARE and replicated at five
organic farms across the state of Maryland.
Bull, who in 2002 conducted a survey of ARS scientists
to determine levels of interest and activity in
organic, found that 81 scientists system-wide
were "conducting research in explicitly organic
systems" and another 107 were interested
in organic systems. In January 2005, the agency
convened a meeting in Austin, Texas, to begin
formulating an ARS organic research agenda—a
step that Bull thinks should give a needed administrative
imprimatur to organic research efforts.
In time, Bull says, "we could be the premier
organic research institution that is federally
funded. As long as the scientists on the ground
communicate with one another, we could make quantum
advances in organic theory as well as in production
practices. We should be able to ask the big questions."
Brennan, who also has a total of 22 acres either
certified organic or in transition, agrees there's
a lot of interest in organic agriculture among
agency scientists and administrators and that
the Austin meeting "was an important first
step." A major challenge to establishing
more certified organic research acreage, he feels,
is that particularly for horticultural crops,
"organic management is more intensive, and
so organic research is more expensive."
Because organic management requires different
tools and skills, it will take time for researchers
and technicians—just as it takes time for
farmers—to make the transition. --LS
||"I think for minimum-till organic
systems to work, a rotation out of annual crops and perhaps
even a tillage rotation will be important to lower seed
banks and clean up perennial weeds."
||"We've gotten to the point where
we can say, yes, we can provide on-farm nutrient sources,
but from the standpoint of keeping the N on the farm—that's
still a big challenge."
of one wall of John Teasdale's office at the Beltsville
Agricultural Research Center is occupied by a large-scale
color satellite image of the surrounding area. On it, you
can see how the fields, barns and greenhouses of the USDA
Agricultural Research Service's flagship experiment station
are ringed and threaded by the housing developments, shopping
malls and thruways of greater Washington, D.C.
Teasdale's been here long enough—26 years—to
have witnessed a good deal of that suburban encroachment.
Today, when he walks out the front door of the building that
is home to the Sustainable Agricultural Systems Lab, which
he heads, and looks south, he can see the nearest IKEA rising
above the trees. Although the research station still commands
more than 7,000 acres, and lies adjacent to another 20,000
acres of undeveloped federal property, the pulse of the Beltway
But Teasdale can also testify to other changes over the last
quarter century, changes less glaring and more broadly beneficial.
While his own interests moved toward sustainable agriculture
early on, in more recent years he's seen a dramatic increase
in research related to making agriculture more profitable
for farmers and less damaging for the environment.
"In the 1950s and '60s, ARS did mostly breeding work,"
Teasdale explains. "Now the seed industry has taken over
most of that. I was hired to do tests of chemical weed control
products. Then the molecular biology kick arrived and lots
of people left the field and went into the lab. I was pretty
much left alone out here." But he's emphatically not
alone any more, as a tour of the BARC research fields makes
Originally from Minnesota, Teasdale received his Ph.D. in
agronomy from the University of Wisconsin in 1978 and was
hired by the USDA straight out of graduate school. "Most
of my first six or seven years were spent working with herbicides,"
he recalls, taking chemicals developed for corn and soybeans
and testing their applicability for various horticultural
"Especially for the smaller crops, the liability is
high and the acreage is low, so there's not much incentive
for the companies to invest there," he explains. Teasdale
showed, for instance, that when cantaloupes were grown on
plastic mulch, atrazine could be used between the rows without
causing damage to the crop.
By the mid 1980s, however, Teasdale decided it was time to
stretch his wings. Herbicide companies, he realized, had little
incentive to pursue labeling even if application data were
available. "Only two things I worked on ever got a label,"
he says wryly. He also decided that as a federal employee,
he had a responsibility to pursue research of the broadest
possible long-term benefit—"research that wasn't
being done elsewhere."
Teasdale began by observing that the most effective weed
management strategies involved a combination of chemical and
cultural controls, including planting methods, cultivation
tools and—crucially—cover crops. For Teasdale,
developing horticultural applications for agronomic chemicals
demanded an integrated approach. As he puts it, "You
thought a lot about how the cultural control was affecting
the crop, how the herbicide affected the cultural control.
. . and how to use factors like row spacing and crop density
to speed up the competitiveness of the crop."
Working on cover crops, in particular, drew Teasdale toward
studying the rest of the agroecological system, in all its
beguiling complexity. "Because cover crops have so many
impacts on cropping systems, from soil moisture levels to
soil temperature levels to nutrient movement, one's research
inevitably starts to branch in to all those different areas,"
he observes. "And I think we've barely scratched the
surface when it comes to understanding all those factors."
Interdisciplinary, systems-oriented research
Teasdale's impulse toward multidisciplinary investigation
was facilitated by a reorganization of BARC's human resources
in the late 1990s. Formerly, the researchers were sectioned
off by discipline: weed scientists, soil scientists, vegetable
crop specialists, agronomists, and so on. In 2000, researchers
from all these fields and more were regrouped into the Sustainable
Agricultural Systems Lab, which today consists of about 45
scientists and technicians.
But the scientists were moving toward a systems-oriented
approach well before that. In 1993, Teasdale and his colleagues
set up the Sustainable Agriculture Demonstration Project,
a long-term study focusing on reduced tillage. Because of
the site's topography—a two to 15 percent slope, running
in both directions across the field—the researchers
sought to prioritize soil conservation as well as crop yields
and net returns in their experimental design. They settled
on four different management systems, all applied to a two-year
rotation of corn/winter wheat/soybean:
- a conventional no-till system with standard herbicide
and fertilizer inputs;
- a crown
vetch "living mulch" system developed by Nathan
Hartwig, a professor of weed science at Penn State University,
also with standard herbicide and fertilizer inputs;
- a modified conventional system, in which cover crops were
substituted for some of the herbicide and fertilizer inputs
(hairy vetch before corn and wheat before soybeans);
- an organic, reduced tillage system, with crimson clover
and cow manure substituted for fertilizer inputs and cultivation
for herbicide inputs.
The SADP is now being brought to a close, Teasdale explains,
"because the general outcome was clear." Although
the crown vetch system performed well in years with adequate
rainfall, it did poorly compared to the conventional no-till
in dry years. The cover crop and organic/manure systems did
the best job of returning nutrients and organic matter to
the soil, but the organic system suffered from heavy weed
pressure. This led to lower average yields for the organic
system, although reduced inputs resulted in only slightly
lower net returns—even without the inclusion of an organic
premium. (Detailed results from the SADP can be found in the
American Journal of Alternative Agriculture 15,2: 79-87
Interestingly, Teasdale notes, a post-experiment uniformity
study (conventional no-till corn grown across all plots) is
showing that "the two treatments that did the worst in
themselves"—the crown vetch and organic treatments—"are
giving the best effects now." In other words, they did
the most to build and improve the soil, resulting in healthier
crops and better long-term yields. "What that says is
that the organic system would have done well if we could have
controlled the weeds."
Other long-term organic vs. conventional systems trials,
including The Rodale Institute's Farming Systems Trial and
the Integrated Cropping Systems Trial at the University of
Wisconsin, have used a similar grain crop-based organic system
with similar results, Teasdale points out. "We had too
many weeds because we tried to just take a conventional agronomic
rotation" and make it organic. "We needed a more
diverse rotation with a hay crop. Otherwise, the weeds will
just kept getting worse."
Lessons from the SADP have been folded into BARC's other
long-term trial, known as the Farming Systems Project. The
FSP was also initiated in 1993, but unlike the SADP it began
with a three-year uniformity study in which no-till conventional
corn was grown across the entire site and data were collected
on growth rates, yields, and soil variables. Experimental
plots for the FSP itself were then laid out to maximize homogeneity
Today the FSP consists of five cropping regimens, two conventional
and three organic:
- a conventional, standard tillage three-year corn-soybean-wheat
- a conventional, no-till three-year corn-soybean-wheat
- an organic two-year corn-soybean rotation;
- an organic three-year corn-soybean-wheat rotation;
- an organic four-year corn-soybean-wheat-red clover/orchard
grass hay rotation.
Each system was tested from all possible starting points
within the rotation sequence. All of the systems included
cover crops—rye before soybeans and hairy vetch or crimson
clover (or hay, in the third organic system) before corn.
The organic systems used both standard tillage and reduced
tillage, depending on the year, with cover crops mowed or
rolled prior to no-till planting.
Given the results of the SADP, Teasdale has been especially
interested in the ability of the different organic rotations
in the FSP to manage weeds. What they've found, he explains,
is a "lower seed bank and better weed control of the
most troublesome weeds in our organic plots in the longer,
more diverse rotations." (A full analysis can be found
in Agronomy Journal 96: 1429-35 ). The four-year organic
rotation beginning with hay did the best job of keeping weed
seed bank levels low.
"I think for minimum-till organic systems to work, a
rotation out of annual crops and perhaps even a tillage rotation
will be important to lower seed banks and clean up perennial
weeds," Teasdale concludes.
The many uses of cover crops
Long-term, multidisciplinary field experiments like the SADP
and the FSP require the collaboration of many scientists.
Soil scientist Michel Cavigelli, agronomist Mark Davis, research
chemist Jeff Buyer and microbiologist Patricia Millner are
just a few of Teasdale's colleagues who have worked on these
studies. One of the strengths of BARC and the Sustainable
Ag Systems Lab (SASL) is that they allow and encourage that
kind of interdisciplinary interaction.
Another of Teasdale's colleagues is Aref Abdul-Baki, a plant
physiologist who has done extensive work on warm-season cover
crops such as sunn hemp, and who has sought to develop cover-crop-based
alternatives to methyl bromide for large-scale vegetable growers
in Florida. (Vegetable producers use the soon-to-be banned
chemical as a soil fumigant to eliminate potentially crop-damaging
nematodes.) Together, Teasdale and Abdul-Baki have studied
the allelopathic effects of cover crops like hairy vetch,
demonstrating, for instance, that the most powerful weed suppression
appears to result from a synergy between the phytotoxins released
by the cover crop residue and its action as a physical barrier.
In the field we run into entomologist Don Weber, who came
to BARC four years ago and is currently studying the effects
of cover crop mulches on Colorado potato beetles. "When
I started looking at cover crops and mulches in the 1980s,
that was an effect I noticed right away," comments Teasdale,
referring to reduced CPB damage on mulched potatoes. "I
mentioned it to the entomologists, but nobody was interested.
Now at last we have people like Don, who are interested."
In some parts of the field the difference was dramatically
visible: unmulched plants skeletonized by the fat orange instars;
a few rows away, mulched plants almost untouched. "There
are at least four different things that could be going on,"
Weber explains enthusiastically. The mulch could be changing
the microclimate, for instance by lowering soil temperatures;
it could be altering the biochemistry of the potato foliage;
it could be directly impacting the potato beetle in some way;
or it could be affecting the pest's natural enemies. "There's
a carabid beetle that's a specialist predator on the CPB,"
Weber adds, brushing aside some cover crop residue and pointing
out a small, blue-black beetle.
Elsewhere on the farm, Teasdale tells us, Weber's trialing
potatoes with a variety of different cover crops, including
crimson clover, hairy vetch, and rye, and is also experimenting
with different ways of handling the transition from cover
crop to crop. "Since potatoes go in so early, you don't
get much biomass from the cover crop if you kill it at the
time of planting," Teasdale points out. "Maybe we
can develop a system in which you plant into the standing
cover crop and then mow when the potatoes start to emerge."
In the 1990s, an SASL study of tomatoes grown on hairy vetch
mulches found that the mulched plants senesced significantly
later in the season than unmulched plants. Subsequent experiments
have sought to clarify the underlying mechanism at work. A
key question is how the vetch residue, which is almost completely
decomposed by mid-season, promotes crop plant health at the
end of the season. This year, the researchers are comparing
tomato plots mulched with vetch tops only, vetch roots only,
rye tops, rye roots, black plastic, white plastic, or not
mulched at all.
"We think the effect has to do with more than just the
N levels supplied by the vetch," Teasdale comments. "Dr.
Autar Mattoo, a molecular biologist in our lab, has shown
that the cover crop mulch influences the expression of many
important genes in the tomato plant."
Cover crops and N utilization
A final, fundamental role for cover crops, of course, is
to supply fertility for crops. While it's well established
that cover crops can supply all the nitrogen needed by a cropping
system, much remains to be learned about how best to manage
"That's really what I see as one of the big challenges
of sustainable agriculture," says Teasdale. "We've
gotten to the point where we can say, yes, we can provide
on-farm nutrient sources, which means they're more sustainable
in terms of the environmental costs of being produced elsewhere
and transported to the farm, but from the standpoint of keeping
the N on the farm—that's still a big challenge."
Because nitrogen supplied by cover crops and composts needs
to mineralize in order to become available to crops, calculating
and timing its availability is trickier than with synthetic
N sources. No crop is 100 percent efficient at utilizing available
N, moreover—"corn is only 50 percent efficient
at using available N, and tomatoes are more like 20-30 percent,"
Teasdale notes—so you have to use too much in order
to have enough. The key is to capture the excess before it
can leach out of the system and become a pollutant.
"Say you have 150 pounds of N in a hairy vetch cover
crop, the amount of N that gets taken up by the crop is quite
small. A number of different people have shown that experimentally—a
substantial part is lost to leaching and to the atmosphere.
With manure and compost, it's the same situation. It's a big
challenge to understand the mineralization process, because
it's microbially driven."
One solution, Teasdale continues, is to revise the definition
of optimum crop production, since the yield-response-to-N
curve is not linear—there's a diminishing return as
you add more nitrogen to the system. "People are thinking
now that if you drop back a bit, you would only slightly lower
yields but put significantly less surplus N into the environment."
Another is "to use cover crop mixtures where the combination
of C and N is better balanced, [so] the N becomes temporarily
sequestered," an effect that's fairly well established
scientifically, Teasdale says. The optimum carbon-to-nitrogen
ratio seems to be between 20:1 and 30:1, he adds.
Of course, a lot of farmers do use a rye-vetch mixture as
cover crop, which is a good way to achieve that C:N balance.
Like other researchers working on organic cropping systems,
however, Teasdale is keenly interested in the prospect of
organic no-till, and "for organic no-till, the mixture
is harder to manage," for various reasons. "You
may get more biomass for weed suppression [with a mixture],
but all that additional residue can interfere with planting
operations." If the planting row falls right on the top
of a rye row, moreover, the rye root mass can inhibit germination.
"But none of those problems are insoluble," he
emphasizes. "They just require more work." Fortunately,
BARC has a dedicated team tackling them from a broad range
of disciplinary perspectives.
Laura Sayre is senior writer for NewFarm.org.